Hello everyone-

I have a 2002 Lightning that has developed a no start problem. It will mostly turn over without starting, however it will occasionally fire up upon initial turn of the ignition or after a long crank. It will mostly fire up if I apply slight amount of pressure on the gas pedal (1/8-1/4 throttle) before turning the ignition. Once it starts it runs and accelerates normally. No hesitation or bogging down.

Other important info-

Has a brand new fuel filter installed.
Fuel pressure is around 36psi.
Battery is fully charged.
Once started it idles normally.

Any suggestions on trouble shooting this problem will be greatly appreciated.

Thanks!

 

Sticky IAC. Just keep starting it with your foot slightly on the gas till you fix it.

 

Is there a way to confirm it's the IAC without just changing parts?

Can the TPS be ruled out as the problem?

 

• https://www.wikihow.com/Check-an-Idle-Air-Control-Valve

 

Best not to begin guessing but understand the cold and hot starting strategy.
Key On powers up the computer and runs the fuel pump a few seconds, then stops the pump.
At the same time the coolant temp value is noted and the air temp is noted.
This sets the ignition timing and fuel richness plus opens the IAC for extra air that raises the Idle speed.
At cranking, the fuel pump is turned on again full time.
.
Hot starts are exactly the same with the exception the engine is already hot or quite warm as detected by the two sensors above so the computer sets different values.
.
All you do by adding throttle is a bit more air. It has no effect adding more fuel because it's fuel injection.
.
If the engine is flooded, holding the gas pedal fully open >>stops<< fuel injection to allow the cylinders to clean out during cranking.
The Throttle Position Sensor has no effect otherwise but shut FI off at near full open throttle signal during cranking.
You have to trouble shoot the system as above to find the failure and not throw parts at it trying to get lucky.
Could be the CHT, IAT, IAC.
Is the engine flooding?
Is it a lack of fuel?
Is it the ignition switch?
Is it a dirty Crank Sensor plugup?
Is it the PCM relay or the fuel pump relay? etc.

 

Does the fact that the truck will fire up (most of the time) if I apply a slight amount of throttle before turning the ignition mean anything? I understand fuel flow is not affected.

 

It could if the IAC is not opening by computer command for some reason.

 

I have had a similar problem on an 03 SuperCrew for five years. I can't point you to a solution but maybe I can set your mind at ease. It's been nothing more than a minor annoyance. That SuperCrew has a 2 or maybe 3 valve 4.6 Windsor, and, of course, is normally aspirated. We might have similar issues or it could be like comparing apples to oranges.

 

With my particular truck, should the RPM needle move while the starter is turning over the motor?

Mine does not move on long crank no start.

 

Finally resolved. Notes from the repair shop.

When engine does not start, there is no RPM signal, no injector and spark pulse.
The crankshaft position sensor signal at the PCM (main computer) is good.
Voltage at the coils and injectors test good. The main relay tests good.
The PCM has an internal issue and needs to be replaced.

Luckily I was able to source a replacement ECU.

 

When my 02 had a similar problem, it was caused by the PCM relay.